Apparatus for mixing and unloading pulverulent material

ABSTRACT

Apparatus for mixing and unloading pulverulent material stored in a silo comprising a plurality of aeration troughs positioned end to end in the floor of said silo forming at least one row therein. Said aeration troughs include self-contained air tight compartments for conducting air from one aeration trough to another thereby eliminating the necessity of separate air piping. The aeration troughs and air conducting compartments contained therein are connected together by means of resilient tubular connectors slidably secured to openings in the ends of said troughs.

United States Patent lnventors Appl. No. Filed Patented AssigneeAPPARATUS FOR MIXING AND UNLOADING [56] References Cited UNITED STATESPATENTS 2,565,835 8/1951 Adams 302/53 2,815,987 12/1957 Sylvest 302/29Primary Examiner-Andres H. Nielsen AtmrneyDunlap, Laney, l-lessin &Dougherty ABSTRACT: Apparatus for mixing and unloading pulverulentmaterial stored in a silo comprising a plurality of aeration troughspositioned end to end in the floor of said silo forming y g at least onerow therein. Said aeration troughs include selfrawmg contained air tightcompartments for conducting air from one 11.8. C1 302/29, aerationtrough to another thereby eliminating the necessity of 302/52 separateair piping. The aeration troughs and air conducting Int. Cl B65g 53/04compartments contained therein are connected together by Field of Search302/29,?11, means of resilient tubular connectors slidably secured in52, 53, 17 openings in the ends of said troughs.

t ?& o g@ o I. 24' l 24/ f/O a2 /4 30/ 25 '28 28 a? 4 l2 /2 /8 2 1PATENTEDFEBl 6197i sum 1 or 2 INVENTOBS .I 1 [ET-i 4. 1 SPEEC BY c/oH/vF0 A4450 BACKGROUND OFTI-IE INVENTION 1. Field of the Invention Thepresent invention relates generally to apparatus for mixing andunloading pulverulent material, and more particularly, but not by way oflimitation, to improved apparatus for mixing and unloading pulverulentmaterial stored in a silo comprising a plurality of aeration troughspositioned end to end in the floor of the silo forming at least one rowtherein.

2. Description of the Prior Art Many various types of apparatus havebeen developed for mixing and unloading pulverulent material from asilo. Commonly, such apparatus include one or more rows of aerationtroughs disposed in the floor of the silo, each row including one ormore separate aeration troughs having air permeable tops. Compressed airis distributed to each such aeration trough by separate conduitsterminating within each aeration trough. Prior to the present invention,it has been necessary to provide relatively deep trenches in the floorof a silo to contain the air piping and aeration troughs mentionedabove. Particularly where the floor of the silo is constructed ofconcrete, considerable labor and expense are required to form suchtrenches. Additionally, the installation of air piping in the trenchesand connection of the air piping to each individual aeration trough istime consuming and expensive.

SUMMARY OF THE INVENTION The present invention is directed to apparatusfor mixing and unloading pulverulent material in a silo, said apparatusincluding at least one row of two or more aeration troughs positionedend to end in the floor of said silo, each of said aeration troughshaving airtight opposite sides, an airtight bottom, an air permeabletop, a forward end and a rearward end. Each of the aeration troughs hasat least one opening in the rearward end thereof, and has a number ofpairs of aligned openings in the forward and rearward ends, the numberof pairs of aligned openings in a first of the aeration troughs in therow being equal to the total number of aeration troughs in the row minusone, the second aeration trough in the row and each successive aerationtrough having one less pair of aligned openings in said forward andrearward ends thereof than the aeration trough just preceding it in therow. Separate airtight compartments connecting each pair of alignedopenings in the forward and rearward ends of said aeration troughs aredisposed within said aeration troughs, and means for connecting each ofsaid openings in the rearward end of. the second aeration trough in therow to the openings in the forward end of the first aeration trough inthe row, and for connecting the openings in the rearward end of eachsuccessive aeration trough with the openings in the forward end of theaeration trough just preceding it in the row are provided. Also, meansfor connecting a source of compressed air to each of the openings in therearward end of said first aeration trough are provided.

It is therefore an object of the present invention to provide improvedapparatus for mixing and unloading pulverulent material stored in asilo.

It is a further object of the present invention to provide apparatus formixing and unloading pulverulent material in a silo including aerationtroughs having self-contained airtight compartments for conducting airto each aeration trough in a row.

It is still a further object of the present invention to provideapparatus for mixing and unloading pulverulent material in a siloincluding aeration troughs which may be quickly and inexpensivelyconnected together by means of resilient tubular connectors.

Still a further object of the present invention is to provide apparatusfor mixing and unloading pulverulent material in a silo comprising aplurality of aeration troughs which may be readily installed inrelatively shallow trenches in the floor of said silo.

Other objects and advantages of the invention will be evident from thefollowing detailed description when read in conjunction with theaccompanying drawings which illustrate the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view ofthe lower portion of a concrete silo including the apparatus of thepresent invention.

FIG. 2 is a horizontal sectional view of the silo taken along line 2-2ofFIG. 1.

FIG. 3 is a top view of a row of the apparatus of the present invention.

FIG. 4 is an end sectional view of the apparatus of the presentinvention taken along line 4-4 of FIG. 3.

FIG. 5 is a side sectional view of I the apparatus of the presentinvention taken along line 5-5 of FIG. 3.

FIG. 6. is an end sectional view of the apparatus of the presentinvention taken along line 6-6 of FIG. 3.

FIG. 7 is a top sectional view taken along lines 7-7 of FIG. 4.

FIG. 8 is an end sectional view taken along line 8-8 of FIG. 3.

FIG. 9 is an end sectional view taken along line 9-9 of FIG. 3

FIG. 10 is an end sectional view taken along line 10 -10 of FIG. 3.

FIG. 11 is an end sectional view taken along line 11l1 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2,a concrete silo, generally indicated by the numeral 10, is shown withthe apparatus of the present invention installed in the floor thereof.The apparatus of the present invention basically comprises a pluralityof aeration troughs 12 positioned end to end in one or more trenches 14formed in the floor 16 of the silo 10. A discharge passageway 18 extendsthrough the floor 16 of silo 10 at the center thereof, and the floor 16of silol0 slopes downwardly throughout its entire surface towards thepassageway 18. Connected to the passageway 18 is a conduit 20 which hasa shutoff valve 22 connected to its lower end. Shutoff valve 22 may beany conventional to its lower end. Shutoff valve 22 may be anyconventional large diameter valve suitable for shutting off thegravitational flow of pulverulent material through conduit 20.

The trenches 14 may be formed in the floor 16 of silo 10 through the useof conventional forms when the floor is poured. The trenches arepositioned so that they extend from a point adjacent to passageway 18 toa point near the periphery of the inside surface 24 of the wall 26 ofsilo 10.

The aeration troughs 12 are connected together in each trench 14 byresilient connectors 28 which will be further described hereinbelow. Theaeration trough 12 in each trench l4 closest to the surface 24 of wall26 is connected to distribution valves 32 by conduits 30. Distributionvalves 32 are in turn connected to headers 34. Each of headers 34 areconnected to master conduit 36 by lateral conduits 38. Master conduit 36is connected to conduit 40 which is connected to a source of compressedair (not shown).

Silo 10 may be elevated on footings 42 in order to provide access tovalve 22, and pulverulent material unloaded therefrom, by trucks orother means for conveying the pulverulent material away from the silo10.

For purposes of this disclosure, one row of aeration troughs 12positioned in a trench 14 in the floor 16 of silo 10 will be described.It will be understood, however, that each row of aeration troughs 12 ineach trench 14 in silo 10 is indentical to the row to be described.Referring then to FIG. 3, a row of aeration troughs 12 is shown. As willbe described further herein below, particular silos may contain rows ofa varying number of aeration troughs. For purposes of this disclosure arow containing three of aeration troughs 12 will be described.

The first aeration trough 44 is positioned at the end of the row closestto wall 26 of silo 10. A second aeration trough 46 is positionedadjacent to aeration trough 44 and a third aeration trough 48 ispositioned adjacent to aeration trough 46. As previously described, asource of compressed air is connected to header 34 by conduit 38. Header34 is in turn connected to distribution valves 32 which are connected toaeration trough 44 by conduits 30. Distribution valves 32 may be anyconventional type of valves which can be manually adjusted to bringabout equal distribution of the compressed air through each of conduits30 to aeration troughs 44, 46 and 48.

REferring now to FIGS. 4 and 5, aeration trough 44 basically comprises apair of identical parallel airtight sides 50 and 51 of rectangular shapewhich are attached to an airtight bottom 52, also of rectangular shape.The sides 50 and 51 and bottom 52 are attached to a rearward end 54 ofrectangular shape and forward end 56 identical to rearward end 54. Thesides 50 and 51, bottom 52 and ends 54 and 56 are preferably formed ofmetal and are welded together so that an airtight rectangular enclosureis formed. The sides 50 and 51 include flanged portions 58 and 59respectively at the upper ends thereof, and rearward end 54 and forwardend 56 include flanged portions 60 and 62 respectively at the upper endsthereof. A porous air permeable member 64, which may be stone, denselywoven fabric, such as multiply canvas of the general type used forbuilding, or other suitable air permeable material is attached to flangeportions 58 and 59 of sides 50 and flanged portion 60 of rearward end 54and flanged portion 62 of forward end 56 so that the top of theenclosure defined by sides 50 and 51, bottom 52, rearward end 54 andforward end 56 is completely covered by member 64. Gas permeable member64 may be attached to flange portions 58 and 59 of sides 50 and 51,flange portion 60 of rearward end 54 and flange portion 62 of forwardend 56 by means of bolts or other suitable attaching means (not shown).

As shown in FIG. 4, the rearward end 54 of aeration trough 44 includesopenings 66, 68, and 70. Each of openings 66, 68 and 70 are of identicaldiameter, and are positioned equal distances one from another. Forwardend 56 includes two openings 72 and 74 (FIG. 6), which are of identicaldiameter as openings 66, 68 and 70. Opening 72 in forward end 56 ofaeration trough 44 is positioned in alignment both horizontally andvertically with opening 68 in rearward end 54 of aeration trough 44. Ina like manner, opening 74 of forward end 56 of aeration trough 44 isaligned both horizontally and vertically with opening 70 in rearward end54 of aeration trough 44.

Referring now to FIGS. 4 through 7, a baffle 76 is disposed withinaeration trough 44 on a horizontal plane parallel with bottom 52 ofaeration trough 44. Baffle 76 is welded to side 50, rearward end 54 andforward end 56 of aeration trough 44. It should be noted that baffle 74is welded into aeration trough 44 at a position above openings 68 and 70in rearward end 54 and openings 72 and 74 in forward end 56. A baffle 78is positioned between aligned openings 70 and 74 and 68 and 72 in avertical plane parallel with sides 50 and S1 of aeration trough 44.Baffle 78 is welded to bottom 52, baffle 76, rearward end 54 and forwardend 56. Thus, an airtight compartment within aeration trough 44 isformed communicating opening 70 in rearward end 54 with opening 72 inforward end 56 of aeration trough 44. A second baffle 80 is disposedwithin aeration trough 44 in a vertical plane parallel with baffle 78.Baffle 80 is welded to bottom 52, rearward end 54, forward end 56, andbaffle 76, thereby forming a second airtight compartment which providescommunication between opening 68 in rearward end 54 and opening 72 inforward end 56 of aeration trough 44.

Aeration trough 46 is identical to aeration trough 44 except that itincludes one less pair of aligned openings in its forward and rearwardends and one less compartment providing communication between saidopenings. Referring to FIGS. 8 and 9, aeration trough 46 includes arearward end 82 having openings 84 and 86 disposed therein. Forward end90 of aeration trough 46 includes an opening 88 aligned bothhorizontally and vertically with opening 86 in rearward end 82. A baffle92 is disposed within aeration trough 46 on a horizontal plane parallelwith the bottom 96, which is welded to side 98, rearward end 82 andforward end of aeration trough 46. A second baffle 94 is disposed withinaeration trough 46 on a vertical plane parallel with side 98 betweenopenings 84 and 86 in rearward end 82. Baffle 94 is welded to the bottom96, rearward end 82, and forward end 90 of trough 46, and is welded tobaffle 92. Thus, an airtight compartment is formed within aerationtrough 46 providing communication between opening 86 in rearward end 82and opening 88 in forward end 90 of aeration trough 46. It should benoted that openings 84 and 86 in rearward end 82 of aeration trough 46are positioned to align both horizontally and vertically with openings72 and 74 in forward end 56 of aeration trough 44.

Aeration trough 48 is identical to aeration troughs 44 and 46 exceptthat no aligned openings in its forward and rearward ends are providedand no airtight compartments are disposed therein. Referring to FIGS. 10and 11, the rearward end 100 of aeration trough 48 includes an opening102 and the forward end 104 of aeration trough 48 doesnot include anyopenings. Opening 102 in rearward end 100 of aeration trough 48 ispositioned to provide alignment both vertically and horizontally withopening 88 in forward end 90 of aeration trough 46.

Referring again to FIGS. 3 through 6, the openings 66, 68 and 70 inrearward end 54 of aeration trough 44 are connected to conduits 30.Conduits 30 may be welded to rearward end 54 of aeration trough 44positioned concentrically over openings 66, 68 and 70 thereby providingairtight connections between conduits 30 and rearward end 54 of aerationtrough 44. Openings 72 and 74 in forward end 56 of aeration trough 44are connected to openings 84 and 86 in rearward end 82 of aerationtrough 46, and opening 88 in forward end 90 of aeration trough 46 isconnected to opening 102 in rearward end 100 of aeration trough 48, bymeans of resilient connectors 28.

Referring particularly to FIG. 5, one of resilient connectors 28 isshown. Each of resilient connectors 28 basically comprises a tubularbody member 106 having a forward portion 108 and a rearward portion 110.Forward portion 108 includes a groove 112 around its entire outerperiphery on a plane perpendicular to the axis of tubular member 106.Rearward portion 110 includes a like groove 114 around its entire outerperiphery on a plane perpendicular to the axis of tubular member 106.Forward portion 108 of tubular member 106 is slidably secured withinopening 84 in rearward end 82 of aeration trough 46 with groove 112engaging the entire inside periphery of opening 84. Rearward portion 110is slidably secured within opening 72 of forward end 56 of aerationtrough 44 with groove 114 engaging the entire periphery of opening 72.Due to the fact that tubular member 106 is formed of resilient material,forward portion 108 and rearward portion 110 may be readily insertedinto openings 84 and 72. Thus, airtight connections are provided betweenthe openings described above in the forward and rearward ends ofaeration troughs 44, 46 and 48.

OPERATION AND CONSTRUCTION As will be understood by those skilled in theart, the size and number of aeration troughs l2 utilized in a row, andthe number of rows required in a particular silo depends on designfactors such as the size and diameter of the silo, the density of thepulverulent material to be stored in the silo, etc. A basic designrequirement is that sufficient aeration trough surface area and volumeof compressed air are provided in the silo to bring about fluidizationof the pulverulent material contained within the silo.

Referring to FIGS. 1 and 2, let it be assumed that silo 10 is filledwith pulverulent material and it is desired to unload a portion of thepulverulent material from the silo. A truck or other conveying means ispositioned under valve 22 which is opened. Compressed air is thenintroduced into conduit 40 from where it is conducted to distributionvalves 32 as previously described. Distribution valves 32 serve todistribute the compressed air in equal volumes into each of conduits 30and into each of the aeration troughs 12. Distribution valves 32 may bemanually adjusted to bring about the desired air distribution prior tostoring pulverulent material in silo 10. From conduits 30, an equalvolume of air is conducted to each of aeration troughs 12 in each row bymeans of the airtight compartments disposed within the aeration troughs12, and the resilient connectors 28 connecting the aeration troughs 12in each row, described above. That is, one-third of the volume of airdelivered to each row of aeration troughs is distributed to eachaeration trough. From within each aeration trough the air passesupwardly trough the air permeable top of each aeration trough insufficient volume and velocity to bring about the fluidization of thepulverulent material contained in silo 110. As is well known in the art,once the pulverulent material has been fluidized by the air, it takes onthe characteristics of a fluid. Thus, due to the slope in floor 16 ofsilo towards opening 18 and discharge valve 22, the fluidizedpulverulent material will flow by gravity into opening 18, throughconduit 20 and through discharge valve 22.

lf it is desired to mix or homogenize pulverulent material contained insilo 10, without unloading the material, discharge valve 22 may bemaintained in a closed position while air is passed into the silo 10through aeration troughs 12. The pulverulent material contained withinsilo 10 will be fluidized and caused to move about within silo l0thereby bringing about mixing of the pulverulent material within silo10.

In construction of a silo including the apparatus of the presentinvention, relatively shallow trenches may be formed in the floorthereof by conventional means. A first aeration trough 12 may 12 maythen be placed in each trench near the periphery of the walls of thesilo and welded to conduits 30. Successive aeration troughs 12 may thenbe placed in each trench and simply and easily connected together bymeans of resilient connectors 28. Due to the fact that the air isconducted to each successive aeration trough through airtightcompartments formed by baffles within the preceeding aeration trough,separate air pipingis not required beneath the aeration troughs. Thus,considerably less time and labor are required for construction oftrenches for the apparatus of the present invention compared to priorapparatus. Additionally, through the use of the resilient connectors 28very little labor is required to complete an entire installation of theaeration troughs of the present invention bringing about a furthersavings of time and labor.

The present invention therefore is well adapted to carry out the objectsand attain the ends and advantages mentioned as well as those inherenttherein. While presently preferred embodiments of the invention aregiven for the purpose of disclosure, numerous changes and details ofconstruction and arrangement of parts can be made which will readilysuggest themselves to those skilled in the art and which are encompassedwithin the spirit of the invention disclosed herein.

We claim:

1. ln apparatus for mixing and unloading pulverulent material stored ina silo, said apparatus including at least one row of two or moreaeration troughs positioned end to end in the floor of said silo, eachof said aeration troughs having airtight opposite sides, an airtightbottom, an air permeable top, a forward end and a rearward end, theimprovement comprismg:

each of said aeration troughs having at least one opening in saidrearward end, and having a number of pairs of aligned openings in saidforward and rearward ends, the number of said pairs of aligned openingsin a first of said aeration troughs in said row being equal to the totalnumber of aeration troughs in said row minus one, the second trough insaid row and each successive trough having one less pair of alignedopenings in said forward and rearward ends thereof than the trough justpreceding it in said row;

separate airtight compartments providing communication between each pairof aligned openings in the forward and rearward ends of said aerationtroughs disposed within said aeration troughs;

means for connecting each of said openings in the rearward end of saidsecond aeration trough in said row to the openings in the forward end ofsaid first aeration trough in said row, and for connecting the openingsin the rearward end of each successive aeration trough with the openingsin the forward end of the aeration trough just preceding it in said row;and

means for connecting a source of compressed air to each of said openingsin the rearward end of said first aeration trough.

2. The apparatus of claim 1 wherein said means for connecting each ofsaid openings in the rearward end of said second aeration trough in saidrow to the openings in the forward end of said first aeration trough insaid row, and for connecting the openings in the rearward end of eachsuccessive aeration trough with the openings in the forward end of theaeration trough just preceding it in said row, comprises: elongatedresilient tubular members each having a forward portion and a rearwardportion, said forward portion of said tubular members slidably securedin said openings in said rearward ends of said aeration troughs in saidrow, and said rearward portion of said tubular members slidably securedin said openings in said forward end of adjacent aeration troughs insaid row.

3. The apparatus of claim 2 which is further characterized to includeeach of said elongated resilient tubular members having a first grooveextending around the entire outer periphery of said forward portion ofsaid member, and a second groove extending around the entire outerperiphery of said rearward portion of said member, each of said groovesbeing slidably secured in one of said openings and having a continuoussurface for sealingly contacting the entire inside periphery of saidopenings.

4. The apparatus of claim 1 wherein each of said separate airtightcompartments disposed within said aeration troughs comprises:

a pair of side baffles parallel to each other and parallel to saidopposite sides of said aeration trough, attached to said forward andrearward ends and bottom of said aeration trough; and

a top baffle attached to said side baffles and attached to said forwardand rearward ends of said aeration troughs.

5. Apparatus for mixing and unloading pulverulent material from a silo,said silo having a downwardly sloped floor and having a pulverulentmaterial discharge valve positioned at a low point in said floor,comprising:

a plurality of aeration troughs positioned end to end in said floorforming at least one row extending transversely across said floor tosaid discharge valve;

each of said aeration troughs having airtight opposite sides, anairtight bottom, an air permeable top, a forward end facing saiddischarge valve and a rearward end facing away from said dischargevalve, and having at least one opening in said rearward end, and anequal number of openings in said forward and rearward ends thereof,aligned with each other, the total number of aligned openings in theends of the first of said aeration troughs at the end of said rowopposite from said discharge valve being equal to twice the total numberof aeration troughs in said row minus two, the second aeration troughand each successive aeration trough in said row having one less openingin said forward end and one less aligned opening in said rearward endthereof than the aeration trough just proceeding it in said row;

separate airtight compartments connecting each pair of aligned openingsin said forward and rearward ends of said aeration troughs disposedwithin said aeration troughs;

means for connecting each of said openings in the rearward end of saidsecond aeration trough to the openings in the forward end of said firstaeration trough, and for connecting the openings in the rearward ends ofeach successive aeration trough with the openings in the forward end ofthe aeration trough just proceeding it in said row; and

means for connecting a source of compressed air to each of said openingsin the rearward end of said first aeration trough.

6. The apparatus of claim wherein said means for connecting each of saidopenings in the rearward end of said second aeration trough in said rowto the openings in the forward end of said first aeration trough in saidrow, and for connecting the openings in the rearward end of eachsuccessive aeration trough with the openings in the forward end of theaeration trough just preceding it in said row comprises: elongatedresilient tubular members each having a forward portion and a rearwardportion, said forward portion of said tubular members slidably securedin said openings in said rearward ends of said aeration troughs in saidrow, and said rearward portions of said tubular members slidably securedin said openings in said forward ends of adjacent aeration troughs insaid row.

7. The apparatus of claim 6 which is further characterized to includeeach of said elongated resilient tubular members having a first grooveextending around the entire outer periphery of said forward portion ofsaid member, and a second groove extending around the entire outerperiphery of said rearward portion of said member, each of said groovesbeing slidably secured in one of said openings and having a continuoussurface for sealingly contacting the entire inside periphery of saidopenings.

8. The apparatus of claim 5 wherein each of said separate airtightcompartments disposed within said aeration troughs comprises:

a pair of side baffles parallel to each other and parallel to saidopposite sides of said aeration trough, attached to said forward andrearward ends and bottom of said aeration trough; and

a top baffle attached to said side baffles and attached to said forwardand rearward ends of said aeration troughs.

1. In apparatus for mixing and unloading pulverulent material stored ina silo, said apparatus including at least one row of two or moreaeration troughs positioned end to end in the floor of said silo, eachof said aeration troughs having airtight opposite sides, an airtightbottom, an air permeable top, a forward end and a rearward end, theimprovement comprising: each of said aeration troughs having at leastone opening in said rearward end, and having a number of pairs ofaligned openings in said forward and rearward ends, the number of saidpairs of aligned openings in a first of said aeration troughs in saidrow being equal to the total number of aeration troughs in said rowminus one, the second trough in said row and each successive troughhaving one less pair of aligned openings in said forward and rearwardends thereof than the trough just preceding it in said row; separateairtight compartments providing communication between each pair ofaligned openings in the forward and rearward ends of said aerationtroughs disposed within said aeration troughs; means for connecting eachof said openings in the rearward end of said second aeration trough insaid row to the openings in the forward end of said first aerationtrough in said row, and for connecting the openings in the rearward endof each successive aeration trough with the openings in the forward endof the aeration trough just preceding it in said row; and means forconnecting a source of compressed air to each of said openings in therearward end of said first aeration trough.
 2. The apparatus of claim 1wherein said means for connecting each of said openings in the rearwardend of said second aeration trough in said row to the openings in theforward end of said first aeration trough in said row, and forconnecting the openings in the rearward end of each successive aerationtrough with the openings in the forward end of the aeration trough justpreceding it in said row, comprises: elongated resilient tubular memberseach having a forward portion and a rearward portion, said forwardportion of said tubular members slidably secured in said openings insaid rearward ends of said aeration troughs in said row, and saidrearward portion of said tubular members slidably secured in saidopenings in said forward end of adjacent aeration troughs in said row.3. The apparatus of claim 2 which is further characterized to includeeach of said elongated resilient tubular members having a first grooveextending around the entire outer periphery of said forward portion ofsaid member, and a second groove extending around the entire outerperiphery of said rearward portion of said member, each of said groovesbeing slidably secured in one of said openings and having a continuoussurface for sealingly contacting the entire inside periphery of saidopenings.
 4. The apparatus of claim 1 wherein each of said separateairtight compartments disposed within said aeration troughs comprises: apair of side baffles parallel to each other and parallel to saidopposite sides of said aeration trough, attached to said forward andrearward ends and bottom of said aeration trough; and a top baffleattached to said side baffles and attached to said forward and rearwardends of said aeration troughs.
 5. Apparatus for mixing and unloadingpulverulent material from a silo, said silo having a downwardly slopedfloor and having a pulverulent materiAl discharge valve positioned at alow point in said floor, comprising: a plurality of aeration troughspositioned end to end in said floor forming at least one row extendingtransversely across said floor to said discharge valve; each of saidaeration troughs having airtight opposite sides, an airtight bottom, anair permeable top, a forward end facing said discharge valve and arearward end facing away from said discharge valve, and having at leastone opening in said rearward end, and an equal number of openings insaid forward and rearward ends thereof, aligned with each other, thetotal number of aligned openings in the ends of the first of saidaeration troughs at the end of said row opposite from said dischargevalve being equal to twice the total number of aeration troughs in saidrow minus two, the second aeration trough and each successive aerationtrough in said row having one less opening in said forward end and oneless aligned opening in said rearward end thereof than the aerationtrough just preceeding it in said row; separate airtight compartmentsconnecting each pair of aligned openings in said forward and rearwardends of said aeration troughs disposed within said aeration troughs;means for connecting each of said openings in the rearward end of saidsecond aeration trough to the openings in the forward end of said firstaeration trough, and for connecting the openings in the rearward ends ofeach successive aeration trough with the openings in the forward end ofthe aeration trough just proceeding it in said row; and means forconnecting a source of compressed air to each of said openings in therearward end of said first aeration trough.
 6. The apparatus of claim 5wherein said means for connecting each of said openings in the rearwardend of said second aeration trough in said row to the openings in theforward end of said first aeration trough in said row, and forconnecting the openings in the rearward end of each successive aerationtrough with the openings in the forward end of the aeration trough justpreceding it in said row comprises: elongated resilient tubular memberseach having a forward portion and a rearward portion, said forwardportion of said tubular members slidably secured in said openings insaid rearward ends of said aeration troughs in said row, and saidrearward portions of said tubular members slidably secured in saidopenings in said forward ends of adjacent aeration troughs in said row.7. The apparatus of claim 6 which is further characterized to includeeach of said elongated resilient tubular members having a first grooveextending around the entire outer periphery of said forward portion ofsaid member, and a second groove extending around the entire outerperiphery of said rearward portion of said member, each of said groovesbeing slidably secured in one of said openings and having a continuoussurface for sealingly contacting the entire inside periphery of saidopenings.
 8. The apparatus of claim 5 wherein each of said separateairtight compartments disposed within said aeration troughs comprises: apair of side baffles parallel to each other and parallel to saidopposite sides of said aeration trough, attached to said forward andrearward ends and bottom of said aeration trough; and a top baffleattached to said side baffles and attached to said forward and rearwardends of said aeration troughs.